The present invention relates to an instrument and method for compacting bone chips into the prepared metaphyseal portion of a femoral cavity near the proximal end of the femur. Once the bone chips are compacted with this instrument according to this method, the femoral cavity is conformed to receive a femoral implant stem. The instrument and method of the present invention are intended to provide implant support through augmentation of the proximal cortical shell.
As is well known, it is often necessary to replace the femoral portion of a hip joint prothesis. In the course of such revision surgery, the prior prosthesis is removed from the femur. If cement was used in the prior surgery, such cement is also removed. Techniques for removing the prosthesis and cement are known in the art. Often, after removal of the old prosthesis and cement, the resulting femoral cavity is larger than desired. It is known in the art to use crushed bone graft to fill this resulting cavity. U.S. Pat. Nos. 5,047,035, 5,192,283, and 5,470,336 relate to methods and instruments for performing hip prothesis revision surgery using crushed cancellous bone graft to prepare the cavity for receiving a prosthesis. These patents also disclose various techniques for removing the old cement.
The prior art methods of the '035, '283, and '336 patents employ the use of a guidewire which is placed longitudinally in the cavity and extends into the diaphysis. Crushed bone graft is placed in the cavity, a cannulated tamp is positioned over the guidewire, and the tamp is impacted to compact the bone within the cavity. Successively larger tamps may be used until the cavity is the desired size. The result is a cavity sized to receive a layer of cement and the replacement prosthesis. The crushed bone graft material is sufficiently compacted to provide support for the replacement prosthesis.
The prior art references noted above are incorporated herein by reference for purposes of disclosing the concepts, instruments and techniques involved in removing the prior prosthesis and compacting bone chips to provide a cavity prepared to receive a new prosthesis stem.
The instrument and method of the present invention are provided to facilitate the process of compacting bone chip layers in the femoral cavity by using a single impaction stem, the proximal end portion of which is reduced in size in steps to provide a well compacted wall of bone chips accurately shaped to fit the proximal portion of a prosthesis stem. The instrument and method of the current invention also overcomes the need for a guidewire and cannulations.